In fall, about 21 mammal and bird species worldwide, mostly in northern regions, change their coat or plumage colors from brown to white. White provides camouflage against predators as snow covers the landscape in winter. In spring, these same animals...

They went into the muslin bags easily as we freed them one by one from under the heavy net. Some were stunned, frozen, immobile; others struggled between the strands, exploding with powerful wings when handled. I was a tag-along, a newbie, an invited...